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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of semiempirical MO methods for open-shell systems (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 702-707 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The use of AM1, MNDO, and MNDOC semiempirical MO methods for calculation of heats of formation and ionization potentials of a series of 38 radicals are described. AM1 and MNDO calculations are reported using both half-electron (HE) and Unrestricted Hartree Fock (UHF) wavefunctions. Results show the MNDOC method to give lowest overall errors, being slightly better than the HE-AM1 method. In all cases, the AM1 method shows considerable improvement over MNDO.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090616
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    An investigation of the relative stabilities of the isomers of CF2N2: Comparison of ab initio and MNDO calculations (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 1170-1178 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio SCF calculations at the HF/3-21G level and semi-empirical MNDO calculations have been used to locate the stationary points on the CF2N2 energy surface. Perfluorodiazomethane is predicted to be most stable isomer, but perfluorodiazirine is predicted to lie only ca 41 kJ higher in energy at the SCF level. There are significant differences between the ab initio and MNDO results for the ordering of some of the isomers. Frequency calculations give results in good agreement with the limited experimental data on these molecules.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540080814
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A theoretical study of the rotational isomers of nitrosomethanol by semiempirical (AM1) and ab initio methods (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 9 (1988), S. 212-221 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The conformational potential energy surface as a function of the two internal torsion angles in C-nitrosomethanol has been obtained using the semiempirical AM1 method. Optimized geometries are reported for the local minima on this surface and also for the corresponding points on the HF/6-31G, 6-31G*, and 6-31G** surfaces. All methods predict cis and trans minima which occur in degenerate pairs, each pair being connected by a transition state of Cs symmetry. The AM1 structures are found to compare well with the corresponding ab initio structures. Ab initio HF/6-31G and HF/6-31G* harmonic vibrational frequencies are reported for the cis and trans forms of nitrosomethanol. When scaled appropriately the calculated frequencies are found to compare well with experimental frequencies. The ab initio calculations predict the energy barrier for cis → trans isomerization to be between 5.8 and 6.5 kcal/mol with the trans → cis isomerization barrier lying between 2.3 and 6.5 kcal/mol. The corresponding AM1 energy barriers are around 1 kcal/mol lower in energy. The ab initio calculations predict the barrier to conversion between the two cis rotamers to be very small with the AM1 value being around 1 kcal/mol. Both AM1 and ab initio calculations predict interconversion between trans rotamers to require between 1.2 and 1.4 kcal/mol.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540090305
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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